The broad, long-term objective of this proposal is to understand the pathophysiology underlying altered pain perception in depressed individuals as a way of understanding the neural dysfunction in depression. The specific aims are to (1) test the effectiveness of our recently developed mood induction paradigm that will effectively induce depressed mood in both pain and fMRI experiments, (2) use phasic and tonic pain stimuli to rest the hypothesis that depressed mood potentiates the perception of pain, and (3) use fMRI to test the hypothesis that mood-altered pain perception is accompanied by activity changes in limbic and prefrontal regions. The health relatedness of the project is that an understanding of the underlying pathophysiology of altered pain in depression could lead to the development of new treatment strategies for both depressive disorders and chronic pain. The research designs are (1) test the effectiveness of a mood induction paradigm to induce depressed moods, (2) measure the ability of depressed mood to alter perceived intensity of both phasic and tonic pain stimuli and to reduce tolerance to tonic pain, and (3) use fMRI in phasic pain experiments to compare activity in limbic and prefrontal brain regions during depressed and non-depressed moods. The methods to be used are psychological mood scales, delivery of phasic electric shock and tonic cold pressor pain, and functional magnetic resonance imaging during delivery of pain stimuli in different mood states. [unreadable] [unreadable]